I'm jusy checking my translations of the P&R and SA questions from Chapter 30 with those of the answer key, and there's a discrepancy in the tenses into which some of the verbs are translated. For example,

I would put the differences down to minor errors in the answer key, but in the latter two sentences, the key's translations seems a better fit. I'm thinking perhaps that the subjunctive has something to do with it, but I can't see how. So any suggestions would be helpful.

Quickly is right: videbit is future; the answer key treats it as if it were videbat (imperfect), so that must be a mistake.

Novi and cognovi are perfect tense forms that have a present meaning: 'I know.' The last sentence (SA 12) is a quote from Propertius (2.15.30). And since it's poetry, novit has to be used because scit wouldn't fit the meter (without rearranging the whole line in some way). But if not for that consideration, scit would be roughly equivalent to novit.

Sorry, I meant to post this sooner. Here is what Wheelock's says on (cog)noscere:

"

[pp. 205] There are two common and quite logical exceptions to the rules for sequence of tenses: a historical present main verb (i.e., a present tense used for the vivid narration of past events) will often take a historical sequence subjunctive, and a perfect tense main verb, when focusing on the present consequences of the past action, may be followed by a primary sequence subjunctive (see P.R. 8...).